Toilet system keeps pumping water out?

Toilet system had a leak (a drip) when the on the ball cock is in full position therefore overflowing after sometime would drip which through out the day would be a waste. I turned off the mains tap had a look at it but could not mead it ie just mended the distance of the screw so it turn the flow of water on the ball valve shorter. Did not work so I tryed it again. But now when the mains water is turned but on the water it flowing out of the pipe in the system at a higher rate and when the ball valve is in the right position its not stopping the flow. Have I messed up the pressure in the pipes now? and I know I because of the drip before that I need to replace the part at the ball valve which is damage. Could anyone help about getting the pressure back in the right way or has the system inside needs to be replaced.